This invention concerns improvements related to filtration. More particularly, in a preferred embodiment, this invention relates to improved filters for cigarettes, cigars or other smoking articles which are effective in the removal of certain smoke phase components such as hydrogen cyanide and ammonia.
Methods for selective removal of hydrogen cyanide from cigarette smoke by means of special filter compositions have been proposed. For example, U.S. Pat. No. 3,664,352, discloses alkaline additives such as alkali metal carbonates which may be applied to conventional filter materials to remove any hydrogen cyanide contained in tobacco smoke. Activated carbonaceous material with a surface treatment of copper oxide has also been proposed for hydrogen cyanide removal. U.S. Pat. Nos. 3,251,365, 3,460,543, and 3,355,317 disclose various metal oxides, namely oxides of cobalt, copper, zinc or iron, on a carrier for removal of hydrogen cyanide. U.S. Pat. No. 3,550,600 discloses zinc acetate in admixture with an organic or inorganic base on a smoke filter paper or cellulose acetate filter support which is described as being effective in the removal of various gaseous components, including hydrogen cyanide, from tobacco smoke.
U.S. Pat. No. 3,828,800 discloses certain anion exchange resins which have an affinity for volatile aldehydes as well as the capability to filter other components such as hydrogen cyanide. U.S. Pat. No. 28,858 discloses buffered polyalkyleneimines which exhibit an affinity for smoke acids.
U.S. Pat. Nos. 3,946,101, 3,875,949, and 3,842,070 disclose a complex fluid filter comprising cellulose which has been oxidized by an inorganic metal nitrate. The filter is described as being useful in removing gaseous and particulate components of smoke.
U.S. Pat. No. 3,618,619 discloses filters fabricated from cellulose acetate which has been impregnated with metal oxides of zinc, iron, copper, etc. and are effective in removing hydrogen cyanide.
U.S. Pat. No. 3,417,758 discloses filters containing a water-soluble, weak basic inorganic salt, i.e., sodium or potassium phosphite, which are described as effective in neutralizing hydrogen cyanide in tobacco smoke.
U.S. Pat. No. 4,022,223 discloses salts of copper and nickel complexed with selected aliphatic or aromatic amines which effectively remove hydrogen cyanide from tobacco smoke.
Although many of the aforementioned additives are effective in reducing hydrogen cyanide in smoke, certain disadvantages remain from a smoker's viewpoint. In some instances, volatile flavorants are removed, thus altering the desirable subjective characteristics. In addition, some of the additives may give an off-taste which renders them undesirable for smoking articles. Other of the methods or additives discussed hereinabove are not suitable due to the unstable nature of the compounds used or to the expense in preparing them.
It is, therefore, an object of the present invention to provide a tobacco smoke filter material capable of removing cyanides, and particularly hydrogen cyanide, from tobacco smoke.
A further object of the present invention is to provide a smoking article in combination with a filter material capable of removing hydrogen cyanide from tobacco smoke.
These and still other objects will be discussed more fully in the description of the invention which follows.